NED Abstract

Copyright by Royal Astronomical Society.
2005MNRAS.356.1440D
Group, field and isolated early-type galaxies - I. Observations and nuclear
data
Denicolo, G.; Terlevich, Roberto; Terlevich, Elena; Forbes, Duncan A.;
Terlevich, Alejandro; Carrasco, Luis
Abstract. This is the first paper of a series on the investigation of
stellar population properties and galaxy evolution of an observationally
homogeneous sample of early-type galaxies in groups, field and isolated
galaxies.
Here we present high signal-to-noise ratio (S/N) long-slit
spectroscopy of 86 nearby elliptical and S0 galaxies. Eight of them
are isolated, selected according to a rigorous criterion, which
guarantees a genuine low-density subsample. The present survey has the
advantage of covering a larger wavelength range than normally found in
the literature, which includes [OIII]lambda5007 and H{alpha}, both
lines important for emission correction. Among the 86 galaxies with
S/N >= 15 (per resolution element, for r_e_/8 central aperture), 57
have their H{beta}-index corrected for emission (the average
correction is 0.190 {angstrom} H{beta}) and 42 galaxies reveal
[OIII]lambda5007 emission, of which 16 also show obvious H{alpha}
emission. Most of the galaxies in the sample do not show obvious
signs of disturbances nor tidal features in the morphologies, although
11 belong to the Arp catalogue of peculiar galaxies; only three of
them (NGC 750, 751 and 3226) seem to be strongly interacting. We
present the measurement of 25 central line-strength indices calibrated
to the Lick/IDS system. Kinematic information is obtained for the
sample. We analyse the line-strength index versus velocity dispersion
relations for our sample of mainly low-density environment galaxies,
and compare the slope of the relations with cluster galaxies from the
literature. Our main findings are that the index-{sigma}_0_ relations
presented for low-density regions are not significantly different from
those of cluster E/S0s. The slope of the index-{sigma}_0_ relations
does not seem to change for early-type galaxies of different
environmental densities, but the scatter of the relations seems larger
for group, field and isolated galaxies than for cluster galaxies.